Jet engine silencer

ABSTRACT

In and for a jet propulsion engine having a thrust nozzle adapted to exhaust a propulsive gas jet, said nozzle including wall means longitudinally bounding a hollow central body substantially coaxial with said nozzle, a silencer device for reducing the noise produced by said gas jet, said silencer device comprising means for supplying the inside of said hollow central body with air, and at least one orifice formed in said wall means and through which air from the inside of said hollow central body can discharge into the gas jet exhausting from said thrust nozzle, wherein the improvement comprises, hingedly connected to the central body, at least one adjustable obturating flap movable between a first position wherein it unmasks said orifice and a second position wherein it masks the same and restores a substantially unbroken surface to the longitudinal wall of the central body.

United States Patent [191 Hache et al.

[451 Oct. 7, 1975 JET ENGINE SILENCER [75] Inventors: Jean GeorgesEdouard Joseph Hache, Fontenay-le-Fleury; Jean-Pierre Achille Allioud,Velisy; Claude Charles Doyotte, Le Plessis Robinson, all of France [73]Assignee: Bertin & Cie, Plaisir, France [22] Filed: Aug. 19, 1974 [21]Appl. No.: 499,333

[30] Foreign Application Priority Data Aug. 21, 1973 France 73.30277[52] US. Cl. 181/33 HC; 181/33 l-lD; 60/226; 60/262; 60/264; 239/265.13;239/265.l7

[51] Int. Cl B64d 33/06 [58] Field of Search 181/33 HB, 33 HC, 33 HD,181/43, 51; 60/226, 262, 264;

[56] References Cited UNITED STATES PATENTS 2,987,879 6/1961 Brown181/33 HC UX 3,133,412 5/1964 Westley 131/33 HC UX 3,372,876 3/1968Colville et al 239/265.l3 X 3,422,624 l/l969 Brooks et al. 181/33 HC UXMedawar et al. 239/265.17 X Straight 181/43 [57] ABSTRACT In and for ajet propulsion engine having a thrust nozzle adapted to exhaust apropulsive gas jet, said nozzle including wall means longitudinallybounding a hollow central body substantially coaxial with said nozzle, asilencer device for reducing the noise produced by said gas jet, saidsilencer device comprising means for supplying the inside of said hollowcentral body with air, and at least one orifice formed in said wallmeans and through which air from the inside of said hollow central bodycan discharge into the gas jet exhausting from said thrust nozzle,wherein the improvement comprises, hingedly connected to the centralbody, at least one adjustable obturating flap movable between a firstposition wherein it unmasks said orifice and a second position whereinit masks the same and restores a substantially unbroken surface to thelongitudinal wall of the central body.

10 Claims, 12 Drawing Figures US. Patent 0a. 7,1975 Sheet 1 of 23,910,375

JET ENGINE SILENCER The present invention relates to a silencer devicefor reducing the noise produced by a propulsive gas jet exhausting fromthe thrust nozzle of a jet propulsion engine, said nozzle including wallmeans longitudinally bounding a hollow central body substantiallycoaxial with said nozzle, said silencer device being of the kindcomprising means for supplying the inside of said hollow central bodywith air, and at least one orifice formed in said wall means and throughwhich air from the inside of said hollow central body can discharge intothe said gas jet.

The invention has for its object, firstly, to improve the noiseabatement effect resulting from placing the gas jet in contact with airissuing from the hollow central body and, secondly, to allow ofcancelling this noise abatement effect when it is no longer required.

In accordance with the invention, there is provided, hingedly connectedto the central body, at least one adjustable obturating flap movablebetween a first or operative position wherein it unmasks the aforesaidorifree, and a second or inoperative position wherein it masks the sameand restores a substantially unbroken surface to the longitudinal wallof the central body.

In accordance with an embodiment of the invention, the flap comprises ahollow body having an open up-' stream end which always lies inside saidcentral body, and a likewise open downstream end which when said orificeis masked lies inside the central body and when said orifice is unmaskedprojects into the gas jet.

In accordance with another embodiment of the invention, the silencerfurther includes a generally dihedron-shaped deflector member supportedby the central body and capable of occupying either an operative ordeployed position wherein it projects into the gas jet and its edgeextends substantially transversely to the nozzle axis, the interior ofsaid dihedron then facing downstream, or an inoperative position whereinit is retracted into said central body.

The description which follows with reference to the accompanyingnon-limitative exemplary drawing will give a clear understanding of howthe invention can be carried into practice.

In the drawing:

FIG. 1 is a diagrammatic illustration in axial section of an embodimentof a jet engine silencer, in which a silencing effect is obtained byinjecting fresh air from an air pocket situated inside the central bodythrough orifices formed in the wall thereof, into the gas jet exhaustingfrom the nozzle, said central body being equipped with adjustableobturating flaps;

FIG. 2 is a schematic view in perspective of the central body formingpart of the silencer shown in FIG. 1;

FIG. 3 is a detail view illustrating an alternative embodiment in whichthe silencer is equipped with an air ejector for improving the supply ofthe inside of the central body with air drawn in from outside the jet engine;

FIG. 4 diagrammatically illustrates a further alternative embodiment inwhich the inside of the central body is supplied with air tapped fromthe by-pass flow of a dualflow jet engine;

FIG. 5 diagrammatically illustrates yet another alternative embodimentin which the inside of the central body is supplied with air tapped frombetween two engine compressor stages;

FIG. 6 diagrammatically illustrates still another alternative embodimentin which two obturating flaps cooperate with the same orifice in thecentral body wall, said flaps being shown in their operative orsilencing positron;

FIG. 7 is a view corresponding to FIG. 6 but in which said flaps areshown in their inoperative position;

FIG. 8 diagrammatically illustrates a further alternative embodiment inwhich the obturating flaps assume the form of hollow bodies, said flapsbeing shown in their operative or silencing position;

FIG. 9 diagrammatically illustrates yet another alternative embodimentin which a dihedron-shaped deflecting member projects, in its operativeposition, through an orifice in the central body;

FIG. 10 is a view corresponding to FIG. 9, further depicting flaps formasking said orifice when the dihedron-shaped deflecting member isretracted into its inoperative position;

FIG. 11 diagrammatically illustrates another arrangement of theinvention in which an auxiliary fairing surrounds, in its operative orsilencing position, the central body in the region of the orifice formedtherein; and

FIG. 12 is a view corresponding to FIG. 11 but in which said auxiliaryfairing is in its inoperative position.

In all the figures in the drawing, like parts are designated by likereference numerals.

Reference is first had to FIGS. 1 and 2, in which reference numeral 1designates a jet propulsion engine terminating downstream in a thrustnozzle 2, of axis XX, from which exhausts in operation a gas jet F.

The gas jet F flows through a passage 3 bounded by the nozzle 2, whichnozzle terminates downstream in a discharge edge 2a. A central body 5coaxial with said nozzle extends rearwardly beyond the discharge edge 2athereof. Central body 5 is supported by a cowling 4 through the agencyof hollow streamlined struts 6 extending across the flow passage 3.

The central body 5 has a wall 7 longitudinally bounding a pocket 8 inthe inside of said central body, which pocket is connected through thehollow struts 6 with the surrounding atmosphere, whereby said pocket 8can be supplied with air drawn in from outside the jet engine, as shownby the arrow f.

Means are provided for placing the gas jet F in contact with air issuingfrom the inside of central body 5. These means include at least one butpreferably several orifices 9 fomied in the longitudinal wall 7 of thecentral body and through which air from the air pocket 8 can be injectedinto the gas jet F as shown by the arrow (1).

Adjustable obturating flaps cooperate with the orifices 9 and include,in respect of each orifice 9, a flap l0 hingedly connected to thecentral body 5 and angularly adjustable in relation thereto. In theexample illustrated, each flap 10 is hingedly connected to central body5 about a hinge-pin 11 extending transversely in relation to the nozzleaxis. Each flap 10 includes a wall element 10a adapted to mask theassociated orifice 9 whereby to restore a substantially unbroken surfaceto central body wall 7, and two side walls 10b, 100, substantiallyparallel to nozzle axis XX and interconnected, inter alia, by a stud l2.

Actuating means allow of pivoting the flaps 10 about the hinge-pins 11between an operative position (shown in FIGS. 1 and 2) wherein theorifices 9 are unmasked, and an inoperative position wherein the sameare masked. In the embodiment shown in FIGS. 1 and 2, the actuatingmeans include, in respect of each flap 10, a link 13 having one of itsends hingedly connected to stud 12 and its other end fast with the rod14a of a fluid-operated actuator 14 common to all the flaps and housedinside central body 5.

In operation, when the flaps 10 are in their operative positions shownin FIGS. 1 and 2, they unmask the oriflees 9 and at the same timeproject into the gas jet F whereby to cause the internal cross-sectionalprofile thereof to assume a corrugated outline having a great perimeter.

At the location of each corrugation in said outline, an air jet d isthus injected into said jet through the associated orifice 9. Thegas/air mixing surface is thereby greatly increased, which helps toreduce the noise produced by the gas jet.

When the silencing effect is no longer required, the actuator 4 isoperated in the direction causing the flaps 10 to assume theirinoperative position (not shown) in which they mask the orifices 9 andrestore a substantially unbroken surface to central body wall 7. Theinternal cross-sectional outline of the gas jet F then resumes itsnormal non-corrugated shape and the injection of air through theorifices 9 is stopped.

FIG. 3 relates to an alternative embodiment with respect to FIGS. 1 and2, in which, in order to increase the rate at which air is sucked infrom outside the nozzle, there is disposed within the hollow strut 6 orwithin central body 5 a jet pump or ejector supplied with pressurizedinducing fluid through a conduit 31. Such ejector is preferably of thedivergent fluid-wall type described in the applicants U.S. Pat. No.3,216,653. In cases where nozzle 2 forms part of a turbojet engine,

the said pressurized fluid may advantageously be pressurized air tappedfrom a compressor of such turbojet.

FIG. 4 depicts an alternative embodiment with respect to thoseillustrated in FIGS. 1 to 3, applicable in cases where jet engine I isof the dual-flow or by-pass type and produces a high-pressure and heatedgas flow F and a low-pressure unheated air flow F which is lightlycompressed by an upstream fan 40. In such cases, the air pocket 8 can besupplied with air through one or more conduits 41 each of which isformed with an inlet orifice 41a, disposed in such manner as to tapfresh air from the low-pressure unheated air flow F and an outletorifice 41b opening into said air-pocket. FIG. 5 illustrates anotheralternative embodiment in which the air-pocket 8 is supplied with airthrough a passageway 50 originating between two stages of a multi-stagecompressor and opening into said air-pocket. In the illustrated example,the compressor is of the dualspool type with a low-pressure spool 51 anda highpressure spool 52, and the passageway 50 originates between thetwo compressor spools.

FIGS. 6 and 7 illustrate yet another alternative embodiment with respectto the one depicted in FIGS. 1 and 2, wherein the obturatingflapsinclude, in respect of each orifice 9, a pair of flaps 60 and 61disposed one after the other longitudinally along the nozzle and hingedto the central body, by their upstream and downstream edgesrespectively, about hinge-pins 62 and 63 extending transversely of thenozzle.

Each flap 60 (or 61) includes a longitudinal wall element 60a (or 61a)adapted to mask part of the associated orifice 9 and to thereby restorea substantially unbroken surface to the wall 7 of the central body.

Each flap additionally includes two side walls 601; and 600substantially parallel to the nozzle axis X'X, and each flap 61 ismovable between two fixed side walls 64!) and 640 supported by thecentral body and extending substantially parallel to said axis.

Each flap 60 of a pair of flaps 60, 61 is fast with an actuating arm 65connected through a link 66 to a similar actuating arm 67 fast with thecompanion flap 61, whereby upon one of said flaps (for example flap 60)pivoting towards the nozzle axis the other flap simultaneously pivotsaway therefrom. Each of actuating arms 67 is hingedly connected to theend of the rod 68a of an actuator 68 common to all the pairs of flaps60-61 and housed inside central body 5.

In operation, when flaps 60 and 61 are in their operative position shownin FIG. 6, they unmask the orifices 9, whereby air jets d) are injectedinto the gas jet F to produce a silencing effect. When the silencingeffect is no longer needed, actuator 68 is activated to move the flaps60 and 61 into their inoperative position (shown for example in FIG. 7),thereby masking the orifices 9 and restoring a substantially unbrokensurface to the wall 7 of the central body. The injection of fresh airthrough orifices 9 is then stopped.

FIG. 8 shows yet another alternative embodiment in which each orifice 9formed in the wall 7 of central body 5 cooperates with a flap hingedlyconnected to the central body about a hinge-pin 81 extendingtransversely of the nozzle axis.

Each flap 80 is in the shape of a hollow body having three closed faces80a, 80b and 80c, an open upstream end 80d and a likewise opendownstream end 80a. The upstream end 80d always lies inside theair-pocket 8 irrespective of the position of flap 80.

In operation, when flap 80 is in its operative position (shown in FIG.8) the orifice 9 is unmasked and the downstream end 80e of the flapprojects into the gas jet F. Two jets of fresh air from air-pocket 8towit, a first jet 4), flowing through the flap 80 via its open ends 80dand 80e, and a second jet (1) passing directly through orifice 9areaccordingly injected into the gas jet F to produce a silencing effect.When this effect is no longer required, flap 80 pivots about itshinge-pin 81 until its face 80a masks orifice 9 and restores asubstantially unbroken surface to the wall 7 of the central body.

FIG. 9 illustrates an alternative possible embodiment of the invention.Depicted in the figure is the central body 5 formed with an orifice 9downstream of the discharge edge 2a of nozzle 2. Reference numeraldesignates a deflecting member supported on central body 5 and shaped asa dihedron having an edge 90a.

Responsively to an actuating member 91, deflecting member 90 can occupya deployed operative position (shown in FIG. 9) in which it projectsinto the gas jet F through orifice 9, downstream of the discharge edge2a of nozzle 2. The dihedron edge 90a then extends in a direction havinga component transverse to the nozzle axis, the interior of the dihedronthen facing the downstream end of the jet engine. In this position thegas jet efflux F is divided by dihedron 90 into two partial jets whichmix, on the one hand, with the air jet d) passing through orifice 9 and,on the other, with a stream of air from the surrounding atmosphere thatpenetrates into the dihedron. v

This enhances the silencing effect. When the latter is no longerrequired, deflecting member 90 moves into a retracted inoperativeposition responsively to actuating member 91, in which position it isretracted into the cental body 5.

As shown in Fig. 10, adjustable obturating means cooperating with theorifice 9 are likewise provided in this particular case. In theillustrated example, such obturating means include a pair of flaps 100,101 hingedly connected to central body 5 about hinge-pins 102, 103respectively, each extending in a direction having a component parallelto the nozzle axis. These flaps may occupy either an operative position(shown in FIG. 10) in which the orifice 9 is unmasked, or an inoperativeposition (not shown) in which said orifice is masked after thedeflecting member 90 has retracted into the central body.

FIGS. 11 and 12 show an alternative arrangement of the invention. Shownon these figures is the central body 5 formed with an orifice 9 at leastpart of which lies downstream of the discharge edge 2a of nozzle 2. Anauxiliary fairing, the upstream edge 110a of which has a diameter inexcess of the greatest dimension of the downstream portion of the enginecowling 4, is disposed coaxially with the engine.

Actuating means 111 allow of sliding the auxiliary fairing 110 parallelto the nozzle axis whereby to cause it to occupy either an extendedposition (shown in FIG. 11 in which it is positioned to form an exhaustdiffuser around the gas jet F, or an inoperative position (shown in FIG.12) in which it surrounds the cowling 4.

In its extended position, auxiliary fairing 110 surrounds central body 5in the region of the orfices 9 (which are then unmasked) and by anejector effect allows of inducing a stream of outside air A into the gasjet F exhausting through the nozzle 2. This enhances the silencingeffect already obtained by injecting streams of air (1) through theorifices 9. When this silencing effect is no longer needed, the flaps 10mask the orifices 9 and auxiliary fairing 110 is moved forward once moreinto its inoperative position shown in FIG. 12.

It goes without saying that changes and substitutions of parts may bemade in the non-limitative exemplary embodiments hereinbefore describedwithout departing from the scope of the invention set forth in theappended claims.

What we claim is:

1. In and for a jet propulsion engine having a thrust nozzle adapted toexhaust a propulsive gas jet, said nozzle including wall meanslongitudinally bounding a hollow central body substantially coaxial withsaid nozzle, a silencer device for reducing the noise produced by saidgas jet, said silencer device comprising means for supplying the insideof said hollow central body with air, and at least one orifice formed insaid wall means and through which air from the inside of said hollowcentral body can discharge into the gas jet exhausting from said thrustnozzle, wherein the improvement comprises, hingedly connected to thecentral body, at least one adjustable obturating flap movable between afirst position wherein it unmasks said orifice and a second positionwherein it masks the same and restores a substantially unbroken surfaceto the longitudinal wall of the central body.

2. A silencer device according to claim 1, wherein the flap comprises ahollow body having an open upstream end which always lies inside saidcentral body, and a likewise open downstream end which when said orificeis masked lies inside the central body and when said orifice is unmaskedprojects into the gas jet.

3. A silencer device according to claim 1, further comprising anadjustable deflecting member in the shape of a dihedron projecting intothe gas jet with its edge extending substantially transversely to thenozzle axis when said orifice is unmasked.

4. A silencer device according to claim 1, wherein the flap is hingedlyconnected to the central body about a hinge line having a componentsubstantially parallel to the nozzle axis;

5. A silencer device according to claim 1, wherein the nozzle comprisesa discharge edge situated upstream of the said orifice.

6. A silencer device according to claim 5, further comprising anauxiliary fairing coaxial with the nozzle, said fairing being disposedat least partly downstream of the said discharge edge and having anupstream diameter greater than the largest dimension of the downstreamportion of a cowling containing the jet engine.

7. A silencer device according to claim 6, further comprising means formoving said auxiliary fairing in a direction parallel to the nozzleaxis, between an extended postion in which the auxiliary fairingfunctions as an exhaust diffuser around the said gas jet and a retracted position in which it surrounds the said engine cowling.

8. A silencer device according to claim 1, wherein the means forsupplying the inside of the hollow central body with air comprise anejector fed with a pressurized inducing fluid.

9. A silencer device according to claim 1, in and for a. jet propulsionengine having an multistage compressor, wherein the means for supplyingthe inside of the hollow central body with air include at least onepassageway originating between two stages of said compressor.

10. A silencer device according to claim 1, in and for a jet propulsionengine of the dual-flow type, namely a heated gas flow and an unheatedair flow, wherein the means for supplying the inside of the hollowcentral body with air comprise means for drawing air from said unheatedair flow.

1. In and for a jet propulsion engine having a thrust nozzle adapted toexhaust a propulsive gas jet, said nozzle including wall meanslongitudinally bounding a hollow central body substantially coaxial withsaid nozzle, a silencer device for reducing the noise produced by saidgas jet, said silencer device comprising means for supplying the insideof said hollow central body with air, and at least one orifice formed insaid wall means and through which air from the inside of said hollowcentral body can discharge into the gas jet exhausting from said thrustnozzle, wherein the improvement comprises, hingedly connected to thecentral body, at least one adjustable obturating flap movable between afirst position wherein it unmasks said orifice and a second positionwherein it masks the same and restores a substantially unbroken surfaceto the longitudinal wall of the central body.
 2. A silencer deviceaccording to claim 1, wherein the flap comprises a hollow body having anopen upstream end which always lies inside said central body, and alikewise open downstream end which when said orifice is masked liesinside the central body and when said orifice is unmasked projects intothe gas jet.
 3. A silencer device according to claim 1, furthercomprising an adjustable deflecting member in the shape of a dihedronprojecting into the gas jet with its edge extending substantiallytransversely to the nozzle axis when said orifice is unmasked.
 4. Asilencer device according to claim 1, wherein the flap is hingedlyconnected to the central body about a hinge line having a componentsubstantially parallel to the nozzle axis.
 5. A silencer deviceaccording to claim 1, wherein the nozzle comprises a discharge edgesituated upstream of the said orifice.
 6. A silencer device according toclaim 5, further comprising an auxiliary fairing coaxial with thenozzle, said fairing being disposed at least partly downStream of thesaid discharge edge and having an upstream diameter greater than thelargest dimension of the downstream portion of a cowling containing thejet engine.
 7. A silencer device according to claim 6, furthercomprising means for moving said auxiliary fairing in a directionparallel to the nozzle axis, between an extended postion in which theauxiliary fairing functions as an exhaust diffuser around the said gasjet and a retracted position in which it surrounds the said enginecowling.
 8. A silencer device according to claim 1, wherein the meansfor supplying the inside of the hollow central body with air comprise anejector fed with a pressurized inducing fluid.
 9. A silencer deviceaccording to claim 1, in and for a jet propulsion engine having anmultistage compressor, wherein the means for supplying the inside of thehollow central body with air include at least one passageway originatingbetween two stages of said compressor.
 10. A silencer device accordingto claim 1, in and for a jet propulsion engine of the dual-flow type,namely a heated gas flow and an unheated air flow, wherein the means forsupplying the inside of the hollow central body with air comprise meansfor drawing air from said unheated air flow.